1. Field of the Invention
The present invention relates to magnetic heads for use in, for example, floating magnetic head devices and, particularly, to a magnetic head having an excellent heat dissipation effect.
2. Description of the Related Art
FIG. 8 is a longitudinal section of a known magnetic head. In FIG. 8, a write head section Hw is an inductive head. This write head section Hw is formed on a read head section Hr that has, for example, a magnetoresistance effect.
This magnetic head is formed on a trailing end surface 1a of a ceramic slider 1 that constitutes a part of a floating magnetic head device. The read head section Hr is disposed on an Al2O3 film 2 formed on the trailing end surface 1a of the slider 1. This read head section Hr detects a magnetic field from a recording medium, such as a hard disc, using the magnetoresistance effect to read a recording signal.
The read head section Hr includes a lower shield layer 3, a lower gap layer 4, a magnetic field reader M1, an upper gap layer 5, and an upper shield layer 6. The magnetic field reader M1 is a magnetoresistive element exemplified by a giant magnetoresistive (GMR) element (typically, a spin valve film), which has a giant magnetoresistance effect; a tunneling magnetoresistive (TMR) element, which has a tunneling magnetoresistance effect; and an anisotropic magnetoresistive (AMR) element, which has an anisotropic magnetoresistance effect.
The lower and upper gap layers 4 and 5 are composed of an insulating material such as Al2O3 and SiO2 while the lower and upper shield layers 3 and 6 are composed of a soft magnetic material with high permeability, such as a Ni—Fe alloy (permalloy).
A separating layer 7 of an insulating material such as Al2O3 and SiO2 is formed on the upper shield layer 6, and the write head section Hw is formed on the separating layer 7.
A lower core layer 10 is formed on the separating layer 7, and a gap-depth-defining layer 11 is formed on the lower core layer 10. The length between the front surface F of the magnetic head facing the recording medium and the front end surface 11a of the gap-depth-defining layer 11 is defined as a gap depth.
A magnetic pole part 12 extends from the front surface F of the magnetic head onto the gap-depth-defining layer 11.
This magnetic pole part 12 includes a lower magnetic pole layer 13, a nonmagnetic gap layer 14 formed on the lower magnetic pole layer 13, and an upper magnetic pole layer 15 formed on the gap layer 14. The upper and lower magnetic pole layers 15 and 13 are composed of a soft magnetic material such as a Ni—Fe alloy.
An insulating layer 17 is formed on the lower core layer 10 on the rear side of the gap-depth-defining layer 11 in the height direction (the Y direction in the drawing). A coil layer 18 that is composed of a conductive material such as Cu and has a spiral pattern is formed on the insulating layer 17. The coil layer 18, which has a double-layer structure, is covered with an inorganic insulating layer 19 and an organic coil-insulating layer 20.
An upper core layer 16 is formed in a pattern by, for example, frame plating and extends over the magnetic pole part 12 and the coil-insulating layer 20. A base end 16a of the upper core layer 16 is connected to a magnetic connecting layer (back gap layer) 21 formed on the lower core layer 10. The upper and lower core layers 16 and 10 are formed by plating with, for example, a Ni—Fe alloy.
A recording current applied to the coil layer 18 induces a recording magnetic field into the lower and upper core layer 10 and 16 to generate a leakage magnetic field between the lower and upper magnetic pole layers 13 and 15, which are separated by the gap layer 14. As a result, a magnetic signal is recorded from the leakage magnetic field to a recording medium such as a hard disc.
In recent years, the size of a magnetic head has been reduced to support recording media with higher recording density. In addition, the read sensitivity of a read head section of a magnetic head has been improved. Accordingly, the read output of the magnetic field reader M1 is largely subject to variations in the magnetic domain structures of the upper and lower shield layer 6 and 3, which are provided above and below the magnetic field reader M1, respectively.
Such variations in the magnetic domain structures of the upper and lower shield layer 6 and 3 are typically caused by heat generated from the coil layer 18 of the write head section Hw and a fluctuating magnetic field generated from the write head section Hw.
Japanese Unexamined Patent Application Publication Nos. 2001-209909 (Page 9 and FIG. 1 of this publication), 2001-236614 (Page 3 and FIG. 1 of this publication), and 2002-216314 (Page 7 and FIG. 7 of this publication) disclose a magnetic head in which metal layers are provided on the rear sides of upper and lower shield layers in the height direction to dissipate heat generated from a coil layer into a ceramic slider.
The magnetic heads in the first and second patent documents, however, are devised only to facilitate the dissipation of heat from the coil layer; they cannot inhibit variations in the magnetic domain structures of the upper and lower shield layers. In addition, these magnetic heads cannot efficiently dissipate heat from the write head sections.